Chokes at a wellhead of an oil and gas well are intended to control the flow from the well. On occasions a breakdown in the operator such as a break in the supply of operating fluid to a pressure responsive operator of the choke may occur. A manual operation of the choke which overrides the operator is desirable.
The prior patent to W. G. Bagle (No. 3,378,224) discloses a gate valve having a valve member which moves responsive to pressure differentials on a piston and also has a manual operator in which a shaft extending through the piston rod is moved by rotation of a hand wheel which rotates a sleeve threaded on the shaft. The movement of the piston moves the valve member and the manual operator.
The T. A. Stehlin U.S. Pat. No. 3,417,960 discloses a piston operated valve with a manual operator normally not threaded into the piston rod. The valve may be opened manually by threading the manual operating rod into the piston rod and continuing rotation opens the valve.
The F. E. Watkins U.S. Pat. No. 3,402,912 discloses a piston operated valve with a manually rotatable shaft threaded through the piston and connected to the valve member for manual movement of the valve member with respect to the piston.
Other patents such as U.S. Pat. Nos. 2,726,790, 2,917,073 and 3,770,029 disclose the use of balls normally retained in parts of a sleeve being cammed into a position between the sleeve part and a recess in an adjoining part to connect the two parts.